Method for making a strong, bulky, absorbent paper sheet using restrained can drying

Abstract

A process for making a strong, bulky, absorbent paper sheet with improved uniformity by forming the web on a forming fabric with a furnish having a consistency in the range of from about 0.08% to about 0.6% solids, dewatering the web noncompressibly such that the web is the range of from about 30% to about 40% dry, transferring the web from the forming fabric to an imprinting fabric, lightly pressing the web and the imprinting fabric against the drying can to form a pattern of densifications in the web, can drying the web from no more than about 30% to 40% dry to at least 55% to 60% dry, and restraining the web between the imprinting fabric and the drying can during the can drying step until the web is at least 55% to 60% dry. In addition to the benefits on uniformity, chemicals added to the furnish such as wet strength resins, dry strength resins, surfactants and dyes will migrate during the drying step to the face of the sheet facing the drying can and, specifically, to the densifications formed in the sheet.

What is claimed: 
     
       1. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 to about 70 pounds per ream comprising the steps of: (a) forming a web on a forming fabric with a furnish;   (b) dewatering the web non-compressively such that the web is at least 8% dry;   (c) transferring the web from the forming fabric to an imprinting fabric by means of a vacuum pick-up;   (d) forming a pattern of densifications in the web;   (e) can drying the web on the surface of at least one can dryer to at least 60% dry such that only one side of the web is placed in contact against the surface of the can dryer during said can drying step;   (f) restraining the web between the imprinting fabric and the surface of at least one car dryer during said can drying step until the web is at least 60% dry; and   (g) maintaining the web in registration with the imprinting fabric during steps d, e, and f such that only a single pattern of densifications is formed in the web.   
     
     
       2. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 further comprising the step of: removing the web from the drying can while the web is still retained on the imprinting fabric.   
     
     
       3. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 2 further comprising the step of: separating the web from the imprinting fabric when the web is at least 90% dry.   
     
     
       4. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: said transferring step is performed with the forming fabric travelling at a faster velocity than the imprinting fabric.   
     
     
       5. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: the vacuum pick-up pulls a vacuum during said transferring step sufficient to conform the web to the topography of the imprinting fabric.   
     
     
       6. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 further comprising the step of: adding to the furnish at least one chemical selected from the group consisting of:   (a) a wet strength resin;   (b) a dry strength resin;   (c) a surfactant;   (d) a debonder;   (e) a dye.   
     
     
       7. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 6 wherein: the majority of said selected chemical added to the furnish during said adding step migrates to the surface of the individual densifications in the web facing the drying can during said can drying step.   
     
     
       8. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 6 wherein: the majority of said selected chemical added to the furnish during said adding step migrates to reside in the densifications in the web proximate to the surface of the web facing the drying can during said can drying step.   
     
     
       9. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: the web is dewatered such that the web is in the range of from about 26% dry to about 32% dry after said dewatering step.   
     
     
       10. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1, wherein: the web is dried to at least 90% dry during said can drying step.   
     
     
       11. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 further comprising the step of: separating the web from the drying can without creping.   
     
     
       12. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: the imprinting fabric includes a pattern of knuckles projecting therefrom, the individual knuckles being spaced apart from one another by a distance not greater than the average fiber length of the furnish.   
     
     
       13. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 further comprising the step of: applying a release to the drying can so that the sheet is not pulled from the imprinting fabric as the web traverses the drying can and as the imprinting fabric exits the drying can.   
     
     
       14. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: said furnish has a consistency in the range of from about 0.08% to about 0.6% solids at the start of said forming step.   
     
     
       15. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: said pattern of densifications is formed in the web by lightly pressing the web and the imprinting fabric against a drying can.   
     
     
       16. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: said can drying step is begun when the web is no more than about 30% dry.   
     
     
       17. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: said can drying step is begun when the web is no more than about 35% dry.   
     
     
       18. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: said can drying step is begun when the web is no more than about 40% dry.   
     
     
       19. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: the imprinting fabric includes a pattern of knuckles projecting therefrom, the individual knuckles being spaced apart from one another by a distance not greater than the average fiber length of the longest fibers in the furnish.   
     
     
       20. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: said forming the web step is performed with a furnish having a consistency in the range of 0.1% to 0.5% solids.   
     
     
       21. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1 wherein: said forming the web step is performed with a furnish having a consistency in the range of 0.1% to 0.2% solids.   
     
     
       22. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 1, wherein: said furnish includes fibers and fines, the majority of said fines migrating to the densifications during said can drying step.   
     
     
       23. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream comprising the steps of: (a) forming a web on a forming fabric with a furnish having a consistency in the range of from about 0.08% to about 0.06% solids;   (b) dewatering the web non-compressively such that the web is in the range of from about 8% to about 34% dry;   (c) transferring the web from the forming fabric to an imprinting fabric by means of a vacuum pick-up;   (d) lightly pressing the web and the imprinting fabric against a drying can to form a pattern of densifications in the web;   (e) can drying the web on the surface of at least one can dryer from no more than 34% dry to at least 55% dry such that only a single side of the web is ever placed in contact against the surface of the can dryer;   (f) restraining the web between the imprinting fabric and the surface of at least one can dryer during said can drying step until the web is at least 55% dry; and   (g) maintaining the web in registration with the imprinting fabric during steps d, e, and f such that only a single pattern of densifications is formed in the web.   
     
     
       24. A process for making a strong, bulky, absorbent paper sheet having a basis weight between about 7 and about 70 pounds per ream as recited in claim 23, wherein: said furnish includes fibers and fines, the majority of said fines migrating to the densifications during said can drying step.